Some environmentalists, however, say Brown's actions don't match his rhetoric -- particularly his recent decision to divert $500 million in cap-and-trade fee revenues away from clean-energy and pollution-abatement projects to help California balance its books.

"The governor is right on the rhetoric, but he needs to put our money where his mouth is," said Bill Magavern, the Coalition for Clean Air's policy director. "That's money that needs to be invested in our communities to reduce pollution and create jobs."

Brown visited Sustainable Silicon Valley's fourth annual Water, Energy and Smart Technology (WEST) Summit at NASA Ames Research Park to showcase a "call to action" signed by more than 500 scientists from 44 nations. The 20-page report addresses five key problem areas: climate disruption, the extinction of species, transformation and loss of ecosystems, pollution, and population growth and consumption.

The document's purpose is to translate scientific lingo into an easy-to-understand message that policy makers, industry and the public can understand.

Brown said that clearly communicating the argument that the world must act now is crucial because news media too often neglect climate change stories in favor of more titillating journalism, while lawmakers won't act unless confronted with concrete, consensus-backed facts.

"We're really in a war here, a contest for ideas, and this crowd is on the losing end," he told the scientists.

Just like in electoral politics, "your base is important, but you've got to convince the swing voter to win," the Democratic governor said.

UC Berkeley biology Professor Anthony Barnosky, in presenting the report to Brown, noted that the governor was "instrumental in spurring us to do this," starting with a phone call Brown made to Barnosky urging him and other climate-change scientists to "shout it from the rooftops."

Magavern and other environmentalists agree, but some say the governor himself needs to do more than just shout.

Sierra Club California director Kathryn Phillips last week said Brown's diversion of the cap-and-trade revenue -- collected under California's landmark law setting limits on greenhouse gas emissions -- means "delaying opportunities to use those funds to actually get critical reductions in global warming pollution at the time when all science shows that we must reduce those emissions as much and as quickly as possible."

Brown didn't talk to reporters at Thursday morning's event. But Evan Westrup, his press secretary, said "the idea is that rather than rushing to spend a large sum of money, this gives them a chance to be smart about how it's spent."

But Magavern said that under laws enacted last year, a plan already is in place for investing the money in areas such as energy conservation, public transit, tree planting and clean energy. "It can be spent on existing programs; we don't have to reinvent the wheel," he said. "We are mystified by the governor's proposal."

The cap-and-trade law isn't the only source of friction between environmentalists and Brown.

Some have criticized his support for loosening some regulations required by the California Environmental Quality Act -- the state's 43-year-old cornerstone of environmental protection -- to encourage economic development, despite concerns from many within his own party.

Many environmentalists also don't like Brown's proposal to build a pair of massive, 35-mile-long tunnels through the Sacramento-San Joaquin River Delta to divert water to Southern California.

In addition, Brown in March said California should examine hydraulic fracturing, or "fracking," to capitalize on the Monterey shale deposit, which the U.S. Energy Department has estimated could hold up to 15 billion barrels of oil -- about 64 percent of the nation's shale oil resources.

Some Democratic lawmakers have sought to ban or heavily regulate fracking, but Brown said the technology shouldn't be rejected out of hand.

"We want to get the greenhouse gas emissions down, but we also want to keep our economy going. That's the balance that's required," Brown said recently while announcing new renewable energy projects.

"The fossil fuel deposits in California are incredible; the potential is extraordinary," he said. "But between now and development lies a lot of questions that need to be answered."

Westrup reiterated that need for answers Thursday, but Magavern said the ultimate answer is reducing fossil-fuel use.

"We need to be kicking the oil habit, weaning ourselves off of our addiction to oil rather than doubling down on dirty fuels," he said.